A cam follower of the generic type, which is configured here as a switchable roller tappet, is described in DE 198 44 202 A1. If, for example, decoupling is to be brought about during a basic circular pass of the cams from the coupling state which is described in FIG. 2 of that DE publication, hydraulic medium is applied in front of the slide-like element as coupling means. In exceptional cases, which need not be explained in greater detail at this juncture, the coupling means may retract only to an insufficient degree (or may assume its coupling position only to an insufficient degree from the decoupled state), so that coupling thus still exists in the edge region. The above-mentioned undesirable coupling can be canceled abruptly during the following cam stroke. This means that the inner unit (pressure piston) moves in the hole direction of the outer unit (housing) in an extremely accelerated manner, with compression of the lost motion spring which is situated between them.
This leads to the lost motion spring moving completely into the blocked position. After a plurality of incorrect switching operations of this type, the lost motion spring becomes seated, causing the disadvantage of its diminished spring force. It can thus occur that the lost motion spring can no longer hold the housing on the receding cam flank during switching off and thus for lost motion.